Sludge collectors are commonly used in wastewater treatment plants to scrape settled sludge from the bottom of a settling tank and to skim floating waste off the surface of the wastewater. The settling tank is typically made of concrete with support tracks or rails in the bottom or floor of the tank and support tracks or rails on the side walls of the tank. The sludge collectors typically include a number of flights which are usually elongated members that extend the width of the tank. The flights are typically pultruded fiberglass in various profiles.
The flights are connected at each of their opposite ends to conveyor chains which carry the flights in a circuit along the bottom of the tank to perform the scraping operation and over the surface of the wastewater to perform the skimming operation. As the flights move along the bottom of the tank, the flights are supported by the rails extending along the tank bottom. As the flights move along the surface of the tank, the ends of the flights are supported by the rails mounted on the side walls of the tank.
The portions of the flights which engage the rails at the bottom and side walls of the tank are subject to wear. To minimize this wear, wear shoes are attached to the flights where the flights contact the rails to thereby protect the flights. Typically, wear shoes are attached to the flights with bolts or other fasteners. However, fasteners are subject to corrosion from exposure to the wastewater, making removal and replacement of worn shoes difficult.
Flights most often have a channel shape in cross-section. Wear shoes for this type of flight generally have a simple L-shape with two holes drilled in each leg of the wear shoe, allowing the wear shoe to be reversed after wear has occurred on one leg. In practice, however, most users simply discard the wear shoe without reversing it. This type of wear shoe is mechanically fastened with bolts and locknuts to the flights. In order to save on hardware, wear shoes can be bolted in-line with the chain attachment plates to utilize common mounting hardware. The hardware is often specified as 304 or 316 stainless steel due to corrosion. Therefore, the cost of flight assembly hardware can be very expensive and can become a significant portion of the overall product cost.
Other prior art wear shoes are available which eliminate the need for mechanical fasteners. These wear shoes allow for manual attachment of the wear shoes onto the flights. However, these prior art wear shoes are useable with only a single flight configuration, a flight having specialized ramps, flanges or protrusions. These designs also rely upon the flexing ability of the flight to allow the wear shoe to be installed.